Really, this is some of you guys' biggest dissapointment of the year? You must either be extremely jaded or not have seen/played or read/heard about much of anything this year.
It's definitely mine, but I got super lucky. The games I banked on were exactly what I'd hoped (games like Mario Kart 8, Super Smash Brothers, Captain Toad, Alien: Isolation, Far Cry 4, and Persona Q) and the games that turned out to be major disappointments (like Assassin's Creed or Master Chief) had no real appeal to me. The only games that were close were inFamous: Second Son (which was actually mostly neat, except that they failed to do the thing that pulled me to inFamous in the first place) and Metal Gear Solid: Ground Zeroes (which plays better than I'd ever hoped and has a bad, mostly non-present story.) I was a little disappointed by Middle-Earth after hearing so much about it, but it's still neat, too.
But Transistor, as I said above, did nothing for me. It's passable and has some well-drawn stuff in a style I like, but the actual things being drawn have no appeal to me. And nothing about the music, story, character control, mechanics, level design, skill tree, or characters ever interested me.